多线切割单晶硅等线损模型及其工艺研究

通过建立等线损切割模型,推算出等线损计算方法,同时研究了不同切割工艺参数对等线损工艺的影响。结果表明:钢线速度越快,回线率越高。切割厚度越大,硅片数越少,回线率越高;同时,等线损工艺能够保证整个加工过程中钢线的磨损量保持基本一致,对于工业化生产具有很好的指导借鉴作用。

Prediction of cavity growth rate during underground coal gasification using multiple regression analysis

During underground coal gasification （UCG）, whereby coal is converted to syngas in situ, a cavity is formed in the coal seam. The cavity growth rate （CGR） or the moving rate of the gasification face is affected by controllable （operation pressure, gasification time, geometry of UCG panel） and uncontrollable （coal seam properties） factors. The CGR is usually predicted by mathematical models and laboratory experiments, which are time consuming, cumbersome and expensive. In this paper, a new simple model for CGR is developed using non-linear regression analysis, based on data from 1 l UCG field trials. The empirical model compares satisfactorily with Perkins model and can reliably predict CGR.

Prediction on adsorption ratio of carbon dioxide to methane on coals with multiple linear regression

The multiple linear regression equations for adsorption ratio of CO2/CH4 and its coal quality indexes were built with SPSS software on basis of existing coal quality data and its adsorption amount of CO2 and OH4. The regression equations built were tested with data collected from some s, and the influences of coal quality indexes on adsorption ratio of CO2/CH4 were studied with investigation of regression equations. The study results show that the regression equation for adsorption ratio of CO2/CH4 and volatile matter, ash and moisture in coal can be obtained with multiple linear regression analysis, that the influence of same coal quality index with the degree of metamorphosis or influence of coal quality indexes for same coal rank on adsorption ratio is not consistent.

Reclaiming the Efficiency of Opportunistic Routing in Wireless Multi-Hop Networks

Opportunistic routing(OR) is an effective way to guarantee transmission reliability in wireless multi-hop networks.However,little research focuses on transmission efficiency.Thus,an analytical model based on open queuing network with Markov chains was proposed to evaluate the efficiency.By analyzing two typical ORs,we find duplicate transmission and collision avoidance overhead are the root reasons behind inefficiency.Therefore,a new scheme called dual priority cooperative opportunistic routing(DPCOR) was proposed.In DPCOR,forwarding candidates are configured with dual priority,which enables the network to classify forwarding candidates more effectively so as to reduce the back-off time and obtain more diversity gain.Theoretical analysis and simulation results show DPCOR achieves significant performance improvement with less time overhead compared with traditional routings and typical ORs.

Recovery of Sillimanite from Beach Sands--An Operator＇s Nightmare？

Sillimanite, chemically named aluminum silicate, 3Al2O3SiO2 is one of the three forms of alumino silicate polymorphs and commonly encountered in aluminous metamorphic, plutonic and volcanic rocks and their weathering products. Traditionally in India, sillimanite is upgraded by froth floatation technique using oleic acid as a collector cum frother, sodium silicate as depressant and soda ash as pH regulator. At TSPL （Trimex Sands Pvt Ltd）, conventional mechanical float cells are installed to float sillimanite. In addition to the usual problems associated with conventional cells, poor flow ability of the sillimanite concentrate is experienced in dry circuit due to the presence of sodium oleate. Fine garnet in the sillimanite concentrate contributes to high iron content in the final product, making sillimanite separation a nightmare for operators （lower recoveries coupled with inferior grades）. Various efforts were made to improve the performance of the circuit such as introduction of additional frother like MIBC （methyl ISO butyl carbinol）, optimizing the operating parameters such as pulp density, collector dosage, depressant dosage, air flow rate, pH etc., use of collector aids, stage wise addition of reagents etc.. The challenges faced to produce a sillimanite product with stringent quality norms and the efforts made to improve the grade and recovery are described in this paper.

Thermal performance of a single U-tube ground heat exchanger:A parametric study

In this research,the thermal performance of a single U-tube vertical ground heat exchanger is evaluated numerically as a function of the most influential flow parameters,namely,the soil porosity,volumetric heat capacity,and thermal conductivity of the backfill material,inlet volume flow rate,and inlet fluid temperature.The results are discussed in terms of the variations of the heat exchange rate,the effective thermal resistance,and the effectiveness of the ground heat exchanger.They show that the inlet volume flow rate,inlet fluid temperature,and backfill material thermal conductivity have significant effects on the thermal performance of the ground heat exchanger,such that by decreasing the inlet volume flow rate and increasing the backfill material thermal conductivity and inlet fluid temperature,the outlet fluid temperature decreases considerably.On the contrary,the soil porosity and backfill material volumetric heat capacity have negligible effects on the studied ground heat exchanger’s thermal performance.The lowest inlet fluid temperature reaches a the maximum effective thermal resistance of borehole and soil,and consequently the minimum heat transfer rate and effectiveness.Also,multilinear regression analyses are performed to determine the most feasible models able to predict the thermal properties of the single U-tube ground heat exchanger.

Change of Nonlinear Heart Rate Variability Indices in Different Seasons

The study investigates the nonlinear heart rate variability indices in different seasons and their dependence on current meteorological factors. The study included 61 relatively healthy student volunteers, their age were 19-23 and they were examined repeatedly in different seasons. The HRV （heart rate variability） recording was performed with the use of the hardware-software complex ＂Varikard 2.51＂ Nonlinear HRV indices were calculated by means of the Kubios HRV 2.1. The following indicators： SD1, SD2, SD1/SD2, D2, DFA, SampEn and quantitative indicators of recurrence analysis （RQA ）---Lmean, Lmax, REC, DET, ShanEn had been analyzed. Statistical analysis was performed using the Statistica 6.0. For the detection of between-group differences were used Repeated Measures ANOVA, and the dependence of nonlinear HRV indices on meteorological was analyzed with the use of multiple non-linear regression. The investigation showed a relative increase in SampEn and the reduction of al in winter and spring seasons, strengthening relationships SampEn correlation with other indicators in the winter season as well as the dependence SampEn on meteorological factors in summer. The detected changes can be considered as the realization of adaptive response of a healthy body.

Hierarchical Cognition Cycle for Cognitive Radio Networks

Cognitive radio(CR) can bring about remarkable improvement in spectrum utilization.Different cognition cycles have been proposed in recent years.However,most of the existing works only emphasize functional or operational aspects of cognition cycle,regardless of other indispensable aspects and the connection between them.To deal with the emerging situation of "data rich,information vague,knowledge poor" in cognitive radio networks(CRNs),we propose the hierarchical cognition cycle(HCC) as a new transdisciplinary research field in this paper.HCC investigates a fundamental problem,which is how to manage available resources in the complex environment to meet various demands in CRN.A comprehensive theoretical framework of HCC is established in terms of the core,the essence loop,the function loop,the operation loop,and the external loop of HCC.The reduction of uncertainty in CRN is studied and several new metrics in HCC are defined.Furthermore,a few research challenges ahead are presented as well.

Kinetics of xylose dehydration into furfural in acetic acid

In this paper kinetics of xylose dehydration into furfural using acetic acid as catalyst was studied comprehensively and systematically. The reaction order of both furfural and xylose dehydration was determined and the reaction activation energy was obtained by nonlinear regression. The effect of acetic acid concentration was also investi- gated. Reaction rate constants were gained. Reaction rate constant of xylose dehydration is kl = 4.189 × 10^10[A]^0.1676 axp （-108.5×1000/RT）, reaction rate constant of furfural degradation is k2=1.271×10^10[A]0.1375 exp （-63.413×1000/RT）and reaction rate constant of condensation reaction is k3-3.4051×10^10[A]0.1676 exp （-104.99×1000/RT）, Based on this, the kinetics equation of xylose dehydration into furfural in acetic acid was set up according to theory of Dunlop and Furfural generating rate equation is d[F]/dt=K1[x]0e-k1t-k2[F]-k3[X]0E-k1 1[F]

STRONG N-DISCOUNT AND FINITE-HORIZON OPTIMALITY FOR CONTINUOUS-TIME MARKOV DECISION PROCESSES

This paper studies the strong n(n =—1,0)-discount and finite horizon criteria for continuoustime Markov decision processes in Polish spaces.The corresponding transition rates are allowed to be unbounded,and the reward rates may have neither upper nor lower bounds.Under mild conditions,the authors prove the existence of strong n(n =—1,0)-discount optimal stationary policies by developing two equivalence relations:One is between the standard expected average reward and strong—1-discount optimality,and the other is between the bias and strong 0-discount optimality.The authors also prove the existence of an optimal policy for a finite horizon control problem by developing an interesting characterization of a canonical triplet.

Detecting Difference Between Coefficients in Linear Model Using Jackknife Empirical Likelihood

Empirical likelihood has been found very useful in many different occasions. It usually runs into serious computational difficulties while jackknife empirical likelihood （JEL） is shown to be effective when applied to some complicated statistics. In this paper, to test the difference between coefficients of two linear regression models, the authors apply JEL to construct the confidence regions. Based on the 3EL ratio test, a version of Wilks＇ theorem is developed. Furthermore, to improve the coverage accuracy of confidence regions, a Bartlett correction is applied. Simulation studies are carried out to show the effectiveness of the proposed method in aspects of coverage accuracy. A real data set is analyzed with the proposed method as an example.

Comparative evaluation of geological disaster susceptibility using multi-regression methods and spatial accuracy validation

Geological disasters not only cause economic losses and ecological destruction, but also seriously threaten human survival. Selecting an appropriate method to evaluate susceptibility to geological disasters is an important part of geological disaster research. The aims of this study are to explore the accuracy and reliability of multi-regression methods for geological disaster susceptibility evaluation, including Logistic Regression(LR), Spatial Autoregression(SAR), Geographical Weighted Regression(GWR), and Support Vector Regression(SVR), all of which have been widely discussed in the literature. In this study, we selected Yunnan Province of China as the research site and collected data on typical geological disaster events and the associated hazards that occurred within the study area to construct a corresponding index system for geological disaster assessment. Four methods were used to model and evaluate geological disaster susceptibility. The predictive capabilities of the methods were verified using the receiver operating characteristic(ROC) curve and the success rate curve. Lastly, spatial accuracy validation was introduced to improve the results of the evaluation, which was demonstrated by the spatial receiver operating characteristic(SROC) curve and the spatial success rate(SSR) curve. The results suggest that: 1) these methods are all valid with respect to the SROC and SSR curves, and the spatial accuracy validation method improved their modelling results and accuracy, such that the area under the curve(AUC) values of the ROC curves increased by about 3%–13% and the AUC of the success rate curve values increased by 15%–20%; 2) the evaluation accuracies of LR, SAR, GWR, and SVR were 0.8325, 0.8393, 0.8370 and 0.8539, which proved the four statistical regression methods all have good evaluation capability for geological disaster susceptibility evaluation and the evaluation results of SVR are more reasonable than others; 3) according to the evaluation results of SVR, the central-southern Yunnan Province are the highest sus-ceptibility areas and the lowest susceptibility is mainly located in the central and northern parts of the study area.